The present invention generally relates to image synthesizing systems, and more particularly to an image synthesizing system comprising an image forming apparatus of an electro-photographic type, the image synthesizing system synthesizing images by using an intermediate transfer belt provided therein.
In a conventional image synthesizing system used in an image processing apparatus such as a copy machine, a plurality of images are synthesized by means of data processing. Such data processing is performed by using a page buffer memory which stores image data corresponding to an entire page of an original. One image datum to be synthesized is first stored in the page buffer memory, and then another image datum to be synthesized is stored in the same page buffer memory, these image data to be synthesized by means of the data processing. The synthesized image may be displayed, if necessary, on a display apparatus so as to confirm whether a desired image has been synthesized. The data of the synthesized image is then supplied to an image forming apparatus so as to output the synthesized image on a recording sheet.
In the above-mentioned image processing for synthesizing the image data, it is previously determined, for an area in which a plurality of images are synthesized, which image is to appear as a basic image and which image is superimposed over the basic image. The image to be superimposed is generally in a blank area of the basic image. When synthesizing two monochromatic images, both images may appear in the same area, that is, one image may overlap the other image.
In recent years, the image processing apparatus has been adapted to handle a multi-color image process and a high-resolution imaging process, and thus capacity of the buffer memory necessary for storing image data has been increased. For example, a memory capacity of 16 megabyte is required for a buffer memory for storing image data of four colors, yellow (Y), magenta (M), cyan (C) and black (K), the image data corresponding to an entire standard A4 size paper. If memory capacity for each image datum to be synthesized is stored in the page buffer memory, the required memory capacity should be further increased. Accordingly, an image forming apparatus using the conventional image synthesizing system is expensive and large in size due to a requirement for a large capacity memory even though RAMs used for memory are highly integrated and a cost thereof has been decreased in recent years.
On the other hand, there is considered an image synthesizing method in which a plurality of toner images are superimposed on a recording sheet by directly transferring those toner images onto the recording sheet one after another. However, this method requires a complex conveying mechanism for conveying the recording sheet to a photoconductive drum after one toner image has been transferred thereto. Additionally, the conveying mechanism becomes more complex in order to achieve accurate positioning of the recording sheet each time the transfer of the toner image is performed. Further, a high quality recording paper is required to eliminate deterioration of the positioning accuracy due to deformation of the recording sheet.